Norman j



Sept. 27, 1960 N. J. SHEERAN 24,881

' LAMINATING ADHESIVE AND METHOD OF PRODUCING THE SAME Original FiledApril 1, 1957 MI 2 t- 2 1? h] j a m '0 n E;

NORMAN J. SHEERAN IN VEN TOR.

(it Luk United States Patent Re. 24,881 Reissued Sept. 27, 1960LAMINATING ADHESIVE AND METHOD OF PRODUCING THE SAME Norman LI. Sheeran,Seattle, Wash., assiguor to American- Marietta Company, Chicago, Ill., acorporation of Illinois 11 Claims. (Cl. 106124) Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsI made by reissue.

This invention relates to improvements in a laminating adhesive and themethod of producing the same; and, more particularly, is concerned witha new protein base adhesive suitable for producing paper-to-paper andpaper-to-wood laminations in high speed continuously operatinglaminating machinery. A typical example of an application of thisinvention is found in the field where paper-skins are bonded to eachside of a piece of wood veneer. The composite laminate thus produced isprimarily used for manufacturing boxes and the like, where ahigh-strength weight ratio is desirable, and substantial waterresistance is a requirement.

In laminating machines of the type mentioned a fastcuring adhesive isnecessary, high water resistance is desirable, and the adhesive must beone which can be applied to the paper webs, or paper skin, by customaryglue-coating rolls. It is also desirable that the adhesive be low incost, and one which'will provide a high strength bond.

A primary object of this invention is to provide an adhesive producingthese desirable results in which the wet phase of the adhesive ismaintainable over a protracted time period but the adhesive is convertedinto the desired bond through the application of momentary heat to alaminated assembly.

A typical paper skin material is 42-lb. kraft linerboard, a paperweighing approximately 42 pounds per thousand square feet. Such a paperis'approximately 0.01 inch thick. The wood veneer with whichconsiderable experience has been had is derived from Douglas fir logsand normally varies between one-tenth and three sixteenth inches inthickness. With such relatively thin paper it is necessary that theadhesive exhibit rapid setting characteristics as otherwise the adhesiveis apt to bleed through the thin paper face, to discolor and disfigurethe same. At the same time it is necessary to have suflicient flowWithin the adhesive that an adequate transfer from the spreader rolls tothe paper web may be obtained and so that the desirable strong andwaterproof bond to the veneer is possible.

,In most of the prior art adhesives used for paper-toveneer bonding theadhesive materials have been either starch, or starch fortified withresins, or isolated protein materials. suitable because they requirecooking during prepara tion and they do not provide sufficient waterresistance unless fortified with an excessive amount of resin. Highresin fortification slows the cure rate of the adhesive and, of course,materially adds to the cost of the adhesive.

The particular machinery to which my adhesive is applicable comprisesmeans establishing a line of edgeto-edge joined Veneer sheets, or acontinuous sheet of wood veneer, above and below which is depositedcontinuous facing sheets of kraft paper. Just prior to the merging of aweb of paper with a face of the veneer, adhesive material is applied byroller means to the inner face of such paper web. The laminate assemblythus formed is passed between heated rolls, at about 20-55 feet perminute during which time the paper webs are pressed into intimatecontact with the veneer, the veneer is flattened and straightened, andthe bond is produced in theadhesive films. Paper-to-paper laminationoccurs at about 300 feet per minute.

The adhesive'of the present invention is based on the use of spray driedanimal blood in a formulation in which a high blood solids to waterratio is maintained. In such a formulation kaolin or china-clay isincorporated to not only reduce the cost through the extension of theblood adhesive base material, but also to improve mixing, to provide anextended pot life, and to control the flow characteristics of theadhesive during spreading and bonding.

Dried animal blood is produced commercially in several forms. Theprimary difference between various 7 blood materials is the temperatureemployed during drying. Highly denatured blood is practically waterinsoluble and generally nondispersible in alkali. Such materials areunsuitable for the present invention. The animal bloods which aresuitable in this invention are those which retain high solubility inwater and are usually produced by spray drying. Bloods produced by otherdrying methods, of which vacuum drying is typical, are likewisesuitable, so long as the water solubility is retained at a high level.In general it may be stated that suitable animal bloods of high watersolubility are those in which there is substantially no denaturation ofthe protein. I have found that my best results. are obtained withsubstantially undenatured spray dried soluble blood having a watersolubility above about 90% and preferably .those above about 92% toabout 95%. Excellent results have been attained by using mixtures ofequal parts of spray dried beef and hog blood. In general r all-beefblood formulations are likewise satisfactory.

v In its broaderaspects my novel method of forming 1 or producing asuitable laminating adhesive for the solids and the water varies betweenabout 110%' and about 250% of the weight of the blood solids. Thisaqueous dispersion is stirred to uniform consistency. Due to the highsolubility of the blood, foaming may occur and must be abated throughaddition of a suitable de-foamer simultaneously with the stirring oragitation of The starch adhesives are not particularly the dispersion.Thereafter the mixture has an alkaline material added to adjust its pHto between about 8 and about 10.3 to produce the glue. The alkalinematerial is preferably one selected from the group consisting of sodiumsilicate, sodium hydroxide and trisodium phosphate and mixtures thereof.It will be noted that I employ a low alkalinity for glues of this type.

Kaolin or china-clay provides full control and extension of theadhesive. This material has been found tobe uniquely useful in thisrespect in that it controls the degree of glue penetration into thepaper as well as into the wood, and insures that the essential glueingredients remain at the glue line where the effective bond isobtained. The clay also functions to control adhesive bonding. Forinstance the use of clay not only provides extension of the glue, i.e.reduces blood content, but it also controls the bonding rate of theadhesive and tends to slow bonding to avoid premature adhesion of thelaminates before the veneers have been flattened and the skins properlystretched.

While I have described above that the kaolin or clay may be added Withthe blood to the water this is immaterial as it is possible to add theclay to the blood-water solution after the same has been made alkaline.From a commercial standpoint it is 'preferable that the dry blood, clayand an anti-foam material be brought together to form a dry glue base.On occasion'through the use of non-hygroscopic alkaline salts the alkalimaterial may likewise be premixed with the other dryingredients.

Alkali-protein solutions when agitatedoften produce a tenacious foamwhich is not onlyidetriniental to proper glue formulation but interfereswith' the spreading of the adhesive and the production of uniformg'luefilms; The abatement'of such foam is "obtainable"through theincorporation of a small amount of'pine oil' fto either the dry gluebase or alternatively 'duringthe wet mixing preparation of the glue. Inaddition to pine oil there are proprietory foam abating materials whichmay be used.

Occasionally it is desirable to incorporate a fungicidal agent toprotein glues to inhibit the growth of destructive fungi or molds at theglue line. These fungicidal materials may be either added to a dry gluepremixor maybe incorporated in a wet glue just prior to the completionof the formulation.

A further desirable Characteristic for the laminating purposes mentionedherein is that the glue maintains a relatively flat viscosity curve overa protracted period of time. This generally referred to'as'pot-life; Inthis specific instance, where the viscosity is measured on a MacMichaelViscometer rotating at 20 r.p.m. using a No. 26 wire, it can be statedthat the initial viscosity range should be between about and about 70Mac- Michael units. The viscosity will gradually increase with time. Theglue is adhesively useful over a wide range of viscosities being limitedonly as to when gelation occurs which of course interferes with pumpingand spreading,

- The viscosities mentioned are particularly low, bearing in mind thehigh blood and clay solids content relative the water ratio asindicated.

to which add N-Grade sodium silicate solution mixed 10 minutes to whichadd Water at 25 C. to adjust the glue viscosity to I between 27-35 MMabout 100 In Example I the clay is 88% of the blood solids and the wateris 192% of the blood solids. The silicate produces pH 9.5. This gluewill remainfluid for a protracted period of time in excess of six hourswhen'held at room temperature.

After formulation, a glue according to Example I was spread on 42-lb.kraft linerboard skins at the rate of 20 pounds of glue per thousandfeet. rate may vary 25% more or less for suitable bonds. The skins wereplaced in opposition to each other at opposite faces of a single pieceof 7". x 7" fir veneer. An additional piece of 90 lb. linerboard wasplaced between the platen and the linerboard tov be bonded to reducethe, heat transfer rate. The test assemblies were then placedin a hotplaten press in which the temperature of the hot platen was 250 C. atpressuresbctween about The spreading EXAMPLE II A glue Mix A wasformulated as follows:

Parts by Ingredients: weight Water at 25 C. 700 Clay 180 Spray driedsoluble blood 600 Pine oil 24 Sodium hydroxide (8.4% solution) 32 Thewater, clay, blood and pine oil ingredientswere placed in a mixingvessel and stirred to uniform consistency. Whereupon the pH was adjustedby the addition of the sodium hydroxide to 8.0. The initial viscositywas 26 MacMichael units on a No. 26 wire at 20 r.p.m. The clay contentby weight is 30% of'the' weight of the blood solids and the total wateris approximately 121% of the blood solids by weight.

A second glue Mix B was produced from a portion of Mix A by addingsuificient sodium hydroxide to adjust the pH to 10.3 whereupon theinitial viscosity was 48 MacMichael units on a No. 26 wire at 20 r.p.m.

A third Mix C was also produced from a portion of Mix A by addingsuflicient sodium hydroxide to adjust the pH to 10.9. The initialviscosity was 130 MacMichael units.

Mixes A, B and C were allowed to stand and viscosity was periodicallychecked to determine the changes occurring with time.

TableA MIX pH Initial Viscosity AElapsed time 8.0 26 38 69 69 79 .86 960 157 217' 295' 405 520' B-E1apsed time 103. 48 70 86 108 0 35' 97 167'243' 350 467' O-Elapsed time 10.9 138 320 Gelled In the accompanyingdrawing Figure 1 is a graph illustrating the viscosity curves of thethree mixes of Table A.

From Figure l and Table A it is to be noted that with glue formulationshaving a pH adjusted to between about 8.0 and about 10.3 the glues havea protracted pot life in excess of eight hours. On the other'hand a gluemix having a pH 10.9 clearly evidences no practical pot life at allbecause gelation occurred within one hour. This abrupt decrease in potlife occurs slightly above pH 10.3 and results in an unspreadablematerial that is not adapted to spreading: at the desirable high speedsof the laminating practices to which this adhesive is adapted.

EXAMPLE III A dry glue base is prepared by intimately mixing thefollowing dry ingredients in the proportions shown:

Ingredients: Parts by weight Kaolin (water washed) "Q. 258 Spray driedsoluble blood (93% water soluble) 306 Tri-sodium phosphate 21 A wet glueis prepared from the dry glue base inthe following manner:

500 parts of Water 2325 C. is placed in a glue mixing vessel and 600parts of dry glue, as described above, is added. The mixture should bestirred for ten minutes. To adjust viscosity, up to 25 parts of watermay then be added. It will be found that the pH is approximately 9.5,and that the initial viscosity of the resulting glue formulation isbetween about and about 60 MM. units on a No. 26 wire, using aMacMichael Viscometer at 20 r.p.m. This viscosity will of courseincrease with time and initially varies with bloods from differentsources.

I have determined that the clay extension of such adhesive may varybetween about 30% and about 90% based on the weight of the blood. With a30% clay extension the water may be approximately 110 to 150% of theblood solids by weight Within the pH range of about 8.0 to about 10.3. A90% clay extension permits water up to 250% of the blood solids byweight.

No heat is employed in the formulation of this glue. The water isnormally added at available temperatures, which are approximately 20 25C. No heat is applied to the glue during formulation. This is importantin this blood glue in order to avoid uncontrollable gelation due to thedenaturation of the soluble blood components. On the other hand the glueis capable of rapid gelation when it is subjected to heat in the wetglue line between the core material, be it a veneer or a cardboard, andthe opposing paper faces being laminated thereto. This rapid gelationproduces instantaneous bonding. A spray dried soluble blood glue havinga high blood solids content relative the water content is entirelypractical for these laminating purposes because it is rapid-setting andproduces, when set, a very highly water resistant bond. The addition ofwell known fungicidal materials commonly used in the laminating art willinsure protection of the glue bond against deterioration from fungi.

Changes and alteration in the method and formulas herein described maybe made within the skill of the art. Those equivalents which fairly fallwithin the spirit of this invention as defined by the appended claimsare covered hereby.

Having thus described my invention, I claim:

[1. The method of making a high speed, heat settable glue forpaper-to-paper and paper-to-wood laminating, comprising: forming anaqueous mixture of a substantially undenatured spray dried soluble bloodand china clay in which the clay varies between about 30% and about 90%of the weight of the blood solids, and the water varies between about110% and about 250% of the Weight of the blood solids; stirring saidmixture to uniform consistency while simultaneously abating foaming;adjusting the pH of said mixture, by the addition of an alkalinematerial selected from the group consisting of sodium silicate, sodiumhydroxide, and trisodium phosphate and mixtures thereof, to betweenabout 8 and about 10.3 to produce a glue having a protracted potlife;and maintaining the glue temperature at approximate room temperature atall times until spread between lamina to be bonded] [2. The method ofclaim 1 in which the pH adjustment is obtained by adding sodiumsilicate] [3. The method of claim 1 in which the pH adjustment isobtained by adding sodium hydroxide] [4. The method of claim 1 in whichthe pH adjustment is obtained by adding trisodium phosphate] 5. Anaqueously dispersible dry glue base, consisting essentially of[comprising]: a mixture of substantially undenatured [spray] dried,water-soluble blood and [china clay] kaolin in which the [clay] kaolinvaries between about 30% and about 90% of the weight of the bloodsolids; a foam abating material; and [an alkali selected from the groupconsisting of sodium silicate, sodium hydroxide, and trisodiumphosphate] a nonhygroscopic 'alka'line salt in an amount to produce a pHbetween about Sand about 10.3 when the dry glue base is dispersedin'water to an initial viscosity of between 10 and ,70 MacMichael unitson a No. 26 wire at 20 r.p.m.

6. A high speed, heat settable laminating adhesive, consistingessentially of [comprising]: a dispersion of 500 parts of water attemperatures of about 2325 C., 276 parts of [china clay] kaolin, 312parts of a substantially undenatured spray dried, water-soluble blood, afoam abating material, and sodium silicate solution in an amount toproduce a pH of between about 8 and about 10.3, said adhesive having aninitial viscosity of about 10 to 70 MacMichael units on a No. 26 wire at20 r.p.m. and incapable of becoming non-spreadaible in about six hoursat approximately room temperature.

7. An aqueously dispersible dry adhesive base mix consisting essentially0 [comprising]: kaolin and spray dried, water-soluble blood in theproportion of between about 30 and about parts of kaolin to parts of theblood solids, solid tri-sodium phosphate in an amount to produce a pH inaqueous dispersion of between about 8.0 and 10.3, and a foam abatingmaterial.

8. The wet adhesive product formed by aqueously dispersing the adhesivebase of claim 7 at room temperature to an initial viscosity of about 10to 70 MacMichael units on a No. 26 wire at 20 r.p.m.

9. The method of making a high speed, heat settable glue forpaper-to-paper and paper-to-wood laminating comprising, uniformlydispersing in water a substantially undenatured dried water-solubleblood, kaolin and alkaline material, said water being present in anamount between about and about 250% of the weight of the blood solids,said kaolin being present in an amount between about 30% and about 90%of the weight of the blood solids and said alkaline material beingpresent in an amount to provide a pH between about 8 and about 10.3,said dispersing operation being effected without substantial addition ofheat to avoid uncontrollable gelation.

10. A method as recited in claim 9 in which a foam abating agent ispresent in said water to preclude undesirable foaming during saiddispersing operation.

11. A method as recited in claim 9 in which said alkaline material isadded to a uniform dispersion of the remaining components specified toadjust the pH within the range specified and said water-soluble blood isa spray dried product soluble in water to an extent of at least about90%.

12. A high speed, heat settable laminating adhesive consistingessentially of an aqueous dispersion of a substantially undenatureddried water-soluble blood, kaolin and alkaline material, said waterbeing present in an amount between about 110% and about 250% of theweight of the blood solids, said kaolin being present in an amountbetween about 30% and about 90% of the weight of the blood solids andsaid alkaline material being present in an amount to provide a pHbetween about 8 and about 10.3.

13. A high speed, heat settable laminating adhesive as recited in claim12 in which said alkaline material is selected from the group consistingof sodium silicate, sodium hydroxide, and tnisodium phosphate andmixtures thereof.

14. A high speed, heat settable laminating adhesive as recited in claim12 in which said adhesive has a viscosity measured at the time ofinitial preparation of about 10 to about 70 MacMichdel units on a No. 26wire at 20 r.p.m.

15. A high speed, heat settable laminating adhesive as recited in claim12 in which said adhesive includes a foam abating material.

(References on following page) 7. 8 References Cited {he file of thispatent 2,400,541 Cone May 21, 1946 or the onglnal @atent 2,413,007 SrereDec, 24, 1946 UNIIED STATELSiPATENiSE; 2,524,309 C0yn e. Opt. 13, 19501,976,436 Cone Oct 9, 1934 2,620,230 P611011 H111- Q- 1952 2350 953 Bainet a1 June 6 44 5 2,874,134 Gossett et a1. Feb, 17,1959

